package cn.sixmillions.mb.sqlSession;

import cn.sixmillions.mb.config.BoundSql;
import cn.sixmillions.mb.pojo.Configuration;
import cn.sixmillions.mb.pojo.MappedStatement;
import cn.sixmillions.mb.utils.GenericTokenParser;
import cn.sixmillions.mb.utils.MyStrUtils;
import cn.sixmillions.mb.utils.ParameterMapping;
import cn.sixmillions.mb.utils.ParameterMappingTokenHandler;

import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.util.ArrayList;
import java.util.List;

/**
 * 执行具体jdbc代码
 */
public class SimpleExecutor implements Executor {

    @Override
    public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {
        // 1. 注册驱动，获取连接
        Connection connection = configuration.getDataSource().getConnection();
        // 2. 转换sql语句
        String sql = mappedStatement.getSql();
        //替换参数 #{xxx}， jdbc识别的是“？”
        BoundSql boundSql = getBoundSql(sql);
        // 3.获取预处理对象：preparedStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());
        // 4. 设置参数
        //参数类型全路径，就是xml中的parameterType
        String parameterType = mappedStatement.getParameterType();
        //根据参数类型全路径，获取class对象
        Class<?> paramtertypeClass = getClassType(parameterType);
        //所有参数
        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            //具体参数名称
            String content = parameterMapping.getContent();

            //反射
            Field declaredField = paramtertypeClass.getDeclaredField(content);
            //暴力访问
            declaredField.setAccessible(true);
            //从传过来的参数对象中获取某个具体参数
            Object o = declaredField.get(params[0]);
            preparedStatement.setObject(i + 1, o);
        }

        // 5. 执行sql
        ResultSet resultSet = preparedStatement.executeQuery();

        // 6. 封装返回结果集
        //返回结果对象的全路径
        String resultType = mappedStatement.getResultType();
        //返回对象的class对象
        Class<?> resultTypeClass = getClassType(resultType);
        ArrayList<Object> objects = new ArrayList<>();
        while (resultSet.next()) {
            Object o = resultTypeClass.newInstance();
            //元数据
            ResultSetMetaData metaData = resultSet.getMetaData();
            for (int i = 1; i <= metaData.getColumnCount(); i++) {
                // 字段名
                String columnName = metaData.getColumnName(i);
                // 字段的值
                Object value = resultSet.getObject(columnName);
                //驼峰转换
                columnName = MyStrUtils.lineToHump(columnName);
                //使用反射或者内省，根据数据库表和实体的对应关系，完成封装
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o, value);
            }
            objects.add(o);
        }
        return (List<E>) objects;
    }

    private Class<?> getClassType(String paramterType) throws ClassNotFoundException {
        if (paramterType != null) {
            Class<?> aClass = Class.forName(paramterType);
            return aClass;
        }
        return null;
    }


    /**
     * 完成对#{}的解析工作：1.将#{}使用？进行代替，2.解析出#{}里面的值进行存储
     *
     * @param sql
     * @return
     */
    private BoundSql getBoundSql(String sql) {
        //标记处理类：配置标记解析器来完成对占位符的解析处理工作
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "}", parameterMappingTokenHandler);
        //解析出来的sql
        String parseSql = genericTokenParser.parse(sql);
        //#{}里面解析出来的参数名称
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();
        BoundSql boundSql = new BoundSql(parseSql, parameterMappings);
        return boundSql;
    }
}
